On Wed, Nov 11, 2009 at 3:10 PM, Jaasiel Ornelas <[email protected]> wrote: > > I'm using: > > Sage Version 4.1.1, Release Date: 2009-08-14
Okay. The above was done with Sage 4.2, so may or may not work in your version. > > We just started laplace in my class, so I did not know that laplace > transforms don't solve non linear ode's. Sorry :p > > On Nov 11, 12:01 pm, David Joyner <[email protected]> wrote: >> On Wed, Nov 11, 2009 at 1:19 PM, Jaasiel Ornelas <[email protected]> >> wrote: >> >> > I can't get desolve_laplace to give me a good output. I had already >> > tried the regular solve (desolve) and it gave to told me that it >> > cannot solve that equation. This is my code: >> >> > sage: (g,t) = var('g,t') >> >> > sage: y=function('y',t) >> >> > sage: DEiii = pi * (39/100*y + 1/2)^2* diff(y,t) + a * sqrt(2*g*y) >> >> This is a non-linear ODE. You can't use Laplace transforms >> to solve such ODEs. >> >> However, it is separable and I can solve a slightly simpler version: >> >> sage: t = var("t") >> sage: y = function("y",t) >> sage: DE = y^2*diff(y,t)+sqrt(y)==0 >> sage: desolve(DE,[y,t]) >> -2/5*y(t)^(5/2) == c + t >> >> Which version of Sage are you using? >> >> >> >> > sage: a = .5^2*pi >> >> > sage: DEiii >> >> > 1/10000*(39*y(t) + 50)^2*pi*D[0](y)(t) + 0.250000000000000*pi*sqrt(g*y >> > (t))*sqrt(2) >> >> > sage: desolve(DEiii, [y,t]) >> > Traceback (most recent call last): >> > ... >> > NotImplementedError: Maxima was unable to solve this system. >> >> > sage: desolve_laplace(DEiii, ["t","y"], [0,50,0]) >> > "?%ilt(-(1521*'laplace('y(t)^2*'diff('y(t),t,1),t,false)+3900*'laplace >> > ('y(t)*'diff('y(t),t,1),t,false)+2500*sqrt(2)*'laplace(sqrt(g*'y >> > (t)),t,false)-125000)/(2500*false),false,t)" >> >> > Perhaps it's because I can't understand the output, but if anyone >> > could help me with this, thank you. > > > --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
